The term "pallet" as used herein means a pallet or other rigid supporting structure which holds a generally planar shape while holding a layer of material and being supported by a fork lift having two spaced forks about 4-6 inches wide, as commonly used to support a load e.g. 36 inches wide, measured in a direction transverse to the direction of extension of the forks.
The term "load" refers to one or more layers of units of material which are combined together for simultaneous handling by a single handling device, such as a fork lift handling a pallet load, a platen truck for handling a unit load on a slip sheet, or a clamp truck for handling a unit load, without a slip sheet, by clamping the load between clamps positioned at the sides of the load.
In my U.S. Pat. No. 4,704,060, I teach a palletizer/load forming system including an in-feed conveyor, a layer forming station, a transfer plate, and a load forming station, all fixed in location such that units of material to be processed must be brought to the in-feed conveyor, and must be delivered to the load forming station. Typically, the units of material are received from a production line. The palletizer/load forming system, as taught therein, is advantageously used where the volume of material coming from a single production line, and/or processed through a single in-feed conveyor justifies the cost of the palletizing equipment. Production line output from more than one line can be combined in one in-feed conveyor, but at the risk of getting the material mixed up on the in-feed conveyor.
In my U.S. Pat. No. 4,988,264, I teach a depalletizing system wherein the depalletizer used is physically very similar in construction to the palletizer taught in U.S. Pat. No. 4,704,060. However, in e.g. FIGS. 1 and 3 of that teaching, I teach the concept of shuttling a plurality of pallet loads into and out of the in-feed position without necessarily emptying any particular load before shuttling in another load. I also teach distributing the depalletized units of material to a plurality of material receiving work stations.
In application Ser. No. 08/076,272, I teach in e.g. FIGS. 11A, 12, and 13, the concept of receiving material into the palletizer from a plurality of in-feed conveyors, forming it into layers at a plurality of layer forming stations, and depositing the material in layers on pallets in a plurality of load forming stations.
The '272 invention greatly improves the cost benefit of mechanizing the palletizing operation where the output of no single production line justifies palletizing equipment, but wherein a combination of production lines, if all fed through one palletizer, does justify the equipment expense.
As shown in the '272 application, the palletizer therein includes a frame superstructure (14) extending substantially the entire width of the palletizer, over all of the load forming stations (76). It would be desirable to eliminate some of the superstructure if the servicing of more than one layer forming station and more than one load forming station could be maintained.
It is an object of this invention to provide a palletizing system, including a mobile transfer vehicle for transferring the layer from the layer forming stationlto the load forming station.
It is another object to provide a palletizing system which includes more than one layer forming station or more than one load forming station, or both, wherein the mobile transfer vehicle is supported by underlying support wheels underlying the frame of the transfer vehicle.
It is a further object to provide a palletizing system wherein underlying support wheels are supported on a track at substantially ground level.
It is another object to provide such a track with a limited length, confined generally to the operating area useful for transferring layers between the layer forming stations and the load forming stations.
It is yet another object to provide a palletizing system wherein the transfer vehicle can move along the track to position the transfer plate to receive a layer from any of the layer forming stations, and to deliver a layer to any of the load forming stations.
It is an object to provide such a palletizing system wherein the transfer plate is disposed for travel along a first path in a direction having a horizontal component, to pick up a layer from a layer forming station, and to deliver a layer to a load forming station, and the underlying support wheels are disposed for travel in a second path, having a horizontal component transverse to the horizontal component of the first path.
It is yet another object to provide a palletizing system adapted to form layers of material at two or more layer forming stations, to receive layers of material at two or more load forming stations, and to transfer the layers between the layer forming stations and the load forming stations using two or more of the transfer vehicles, supported independent from one another, on corresponding two or more sets of wheels, whereby the two or more transfer vehicles can be separately controlled by the controller, and can ply one and the same track.
It is still a further object to provide a method of placing a layer on a pallet, including receiving a layer from a layer forming station onto a transfer plate carried on a supporting frame. Rolling the supporting frame, with transfer plate and layer thereon, along a substantially ground-engaging track, and thereafter transferring the layer from the transfer plate to a pallet in a load forming station.
It is finally an object to sense a layer being formed in a layer forming station, to sense the location of each of the transfer vehicles, and the assignments already given to the transfer vehicles, and to assign pick-up and delivery tasks to the transfer vehicles such that each transfer vehicle actively operates on all of the track which is not occupied at any given time by another transfer vehicle, and which cannot be reached without passing another transfer vehicle.